Mac computer repeatedly prompts for password but small print is about maximum number of connection from user+IP exceeded mail_max_userip_connections=10

When you have these symptoms:

Mac computer repeatedly prompts for password but small print is about maximum number of connection from user+IP exceeded mail_max_userip_connections=10

This error can be witnessed in /var/log/mail.log

tail -f /var/log/mail.log | grep boss

Mar 14 18:19:28 hostname dovecot: imap-login: Maximum number of connections from user+IP exceeded (mail_max_userip_connections=10): user=<[email protected]>, method=PLAIN, rip=a.b.c.d, lip=e.f.g.h, TLS, session=<7nZyCzDaEs0Yudk2>

How to refine the process of isolation

grep -r "mail_max_userip_connections" /etc/dovecot
/etc/dovecot/conf.d/20-imap.conf: #mail_max_userip_connections = 10
/etc/dovecot/conf.d/20-pop3.conf: #mail_max_userip_connections = 10

grep -r is your new best friend

Solution

[[email protected]:/etc/dovecot]> vi conf.d/20-imap.conf

Uncomment that line and change the default. Be conservative, for example, make 10 to be 15. Restart dovecot

Comment

This only appeared to happen on one Macintosh computer out of 1000+ email accounts. It seems the Mac (or that Mac) occassionally overwhelmed the Dovecot server with more than 10 connections from the same IP at once. This seems like a networking error but to preserve the peace (and have less ‘urgent’ customer services) we upped the limit.

Reference

 

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